There is a conventionally suggested storage subsystem that has storage devices and a plurality of controllers for controlling data input to, and output from, the storage devices wherein each controller is connected via a controller-to-controller connection path; and when one controller receives a write command or read command, which should be executed by a controller of the other system, from a host computer, it transfers the received write command or read command to the controller of the other system via the controller-to-controller connection path (see Patent Literature 1).
When one controller of the above-described storage subsystem receives a write command or read command, which should be executed by the controller of the other system, from the host computer, it transfers the received write command or read command to the controller of the other system, thereby writing the write command or read command to a local memory for the other system. So, every time one controller receives a write command or read command, it can process the write command or read command without communicating with other controllers.